Switch having opposed dome and flexible bifurcated contacts

ABSTRACT

In a switch a convex domed contact is opposed to a bifurcated contact consisting of a pair of elements providing contact surfaces spaced from one another and each having a dome contact wiping edge opposed to a portion of the dome contact and supported by a pair of flexible spring supports capable of resilient flexing and twisting so that as the contacts are urged together the spring supports continuously urge each of the contact surfaces into wiping engagement with the dome contact.

United States Patent Lambert et al. 1 I Sept. 5, 1972 [54] SWITCH HAVINGOPPOSED DOME 2,612,367 9/1952 Blomquist ..200/ 166 J AND FLEXIBLEBIFURCATED 3,068,335 12/ 1962 Greg ..200/166 BH CONTACTS 3,270,1568/1966 Stewart ..200/67'D [72] Inventors: James B. I be", Norwalk, Conn;3,286,049 11/1966 Dram ..200/166 Bl-l 3,418,608 12/1968 Angel et a1...335/131 Semen Tappan 3 493 702 2/1970 R 200 166 BH Henry Morgan,westport Conn amstetter [73] Assignee: T-Bar Incorporated, Wilton, P i Ei -H ld Broome conn' Attorney-John C. Dorfman [22] Filed: Sept. 15, 1971[57] ABSTRACT [21] Appl. No.: 180,629

In a switch a convex domed contact 15 opposed to a bifurcated contactconsisting of a pair of elements [52] US. Cl. ..335/133, 200/164,200/166, providing Contact Surfaces Spaced f one another 335/196 andeach having a dome contact wiping edge opposed ..H01h 1/18. to a portionof the dome Contact and Supported by a 1 0 N 2 pair of flexible springsupports capable of resilient 7 D flexing and twisting so that as thecontacts are urged together the spring supports continuously urge eachof [56] References Cited the contact surfaces into wiping engagementwith the UNITED STATES PATENTS dome Contact 2,149,699 3/1939 James et a1..200/164 R 5 Claims, 6 Drawing Figures SWITCH HAVING OPPOSED DOME ANDFLEXIBLE BIFURCATED CONTACTS This invention relates to improvements inswitches and specifically to a configuration of switch contacts whereinone of the contacts is dome-shaped and is opposed by a bifurcatedcontact each part of which is independently flexibly supported. Thisinvention has general utility in switches, and may be used, for example,in switch and relay structures, such as those illustrated in U.S. Pat.No. 3,226,508, granted Dec. 28, 1965, to A. H. Morgan, Walter Uhl andHenry R. Angel, and No. 3,418,608 granted on Dec. 24, 1968, to Henry R.Angel and A. Henry Morgan, both of which patents are assigned toElectronic Controls, Inc.

Particularly in relays and switches which undergo repeated use but areexpected to provide long life, it is important that good electricalcontact having low electrical resistance be made between the switchcontacts each time the contacts are closed. In the prior art, variousexpedients have been used to assure positive and good electricalcontact, such as arranging the contacts so that they do not simply movetoward and away from one another but have some lateral movement toproduce wiping and cleaning of the contacts. Other expedients used toassure good positive contact to include opposing contacts with sharpedges which are arranged transverse to one another. However, such sharpedges have a tendency to flatten with use, leaving switches which areless effective than switches with traditional button contacts. The useof precious metals to improve contacts and lower switch contactresistance has also been employed in a wide variety of applications.However, with all of these expedients that have been available in theprior art, it has been difficult to make a switch which is highlyreliable and gives a repeatable electrical effect over a long period oftime, and particularly one whose contact resistance does not tend tochange either through accumulation of dirt, variation in mechanicalengagement forces or change in condition of the contact surfaces. Inmany applications, a substantial change in contact resistance is highlyundesirable, even though the switch is relatively reliable from thestandpoint of repeatedly closing electrically over a long period oftime.

The present invention provides a switch which has particularapplicability in low level circuits, commonly known as dry circuits, buthas applicability in other applications, as well. It is of the class ofopposed contact switches, but it is more highly reliable than otherswitches of this class and will consistently make good electricalcontact of an essentially constant contact resistance over a long activelife. It has inherent in its structure a contact wiping action in morethan one direction, and, therefore, will maintain clean contacts. At thesame time it provides two very positive contacts, instead of oneinsuring that at least one contact is always closed. As a practicalmatter both contacts always close and the contact resistance of each ofthese contacts remains essentially constant because the nature of thecontact is always the same, even though it may vary in position due tosome minor shifting of the switch parts, due to wear, or for otherreasons.

More specifically, the structure of the present invention involves aswitch employing a pair of contacts, at least one of which is supportedon a resilient support, supported by an insulating supporting framewhich holds the contact support structure and maintains a predeterminedrelationship between said contacts. An actuator means moves at least onecontact relative to the other contact to change switch condition. Inthis structure, one of the contacts is provided with a convexdome-shaped contact area with no flat portions over said area. The othercontact is bifurcated and consists of a pair of elements providingcontact surfaces spaced from one another, and each having a dome contactwiping region opposed to a portion of the dome contact and supported bya pair of flexible spring supports capable of resilient flexing andtwisting such that as the contacts are urged together the flexiblespring supports will continuously urge each of the contact surfaces intowiping engagement with the dome contact. Independently flexing, twistingand yielding is provided by the supports for each contact surface toaccommodate to the position of the other and for accommodating to aposition producing good electrical contact itself.

Preferably the contact areas are coated with precious metal by plating,or otherwise, and preferably the bifurcated contact is an integral partof a long narrow strip provided with a slot extending part way along thestrip to divide the strip into two flexible spring supports, such thateach spring support is sufficiently long and narrow relative to itsthickness to permit needed twisting to accommodate movement necessary tokeep each contact in good wiping condition and good electrical contactwith the dome contact.

In the prior art there have been some convex contacts of various types,but by and large, these have been used in high current circuits as ameans wedged between two relatively massive contacts to provide a highcurrent path from one of said massive contacts to the other. Varioustoggling action has been used with such switch arrangements to completethe wedging action with sufficient force (for example, see U.S. Pat.Nos. 2,743,338 and 2,846,529 to Graybill). There have also been switchesin which pointed contacts have been opposed by ring contacts, such asSchuler U.S. Pat. No. 2,899,515, but the ring contact involved in sucharrangements frequently results in only a single point of contact atsome place along the periphery of the ring and uncertainty about howmuch contact area will be involved and what the electrical contactresistance will be.

A U.S. Pat. No. 2,850,602 to Breese et al. shows a domed contact opposedto a trough in order to give two regions of contact on the dome.However, the effect of ridged connection from one side of the trough tothe other results under certain circumstances in contact occurring onlyat one point and contact at that one point may actually act to hold thesecond region away from the dome. The applicants arrangement, bycontrast, employs two separately supported contact sur faces of thebifurcated contact with separate flexible and yielding supports for eachof the bifurcated contact elements so that the position assumed by eachis independent of the other. The present invention, of course, doesassume that the throw of the switch is sufficient that after the firstone of the bifurcated elements strikes the dome its spring will permitit to yield, twist or slide over the dome until the second contact is inposition. Thereafter both contact elements will yield, twist or slideuntil movement under the influence of their actuator is stopped.

For a better understanding of the present invention, reference is madeto the accompanying drawings in which FIG. 1 is a partial sectional viewthrough a relay assembly of the general type shown in FIG. 1 of U.S.Pat. No. 3,226,508 on a somewhat enlarged scale;

FIG. 2 is a partial sectional view taken along line 2- 2 of FIG. 1;

FIG. 3 is an enlarged view taken along line 3-3 of FIG. 2 showing partof the structure shown in FIG. 1;

FIG. 4 is a plan view from above of a single bifurcated spring switchblade;

FIG. 5 is a further enlarged, somewhat schematic view taken on line 5-5of FIG. 3 showing the contacts open; and

FIG. 6 is a view similar to FIG. 5 showing the contacts closed.

Referring first to FIG. 1, the disclosure of U.S. Pat. No. 3,226,508will be understood to be incorporated by reference to show one possibleswitch or relay, in which the switch of the present invention might beemployed, including various alternative types of actuators. It will beappreciated that such switches can be made with electromagneticactuators, or mechanical operators of various types. The presentinvention has been embodied in switches of this general type but can beembodied in switches of the type shown in U.S. Pat. No. 3,418,608, aswell as switches of many other types.

Referring to FIGS. 1 and 2, a relay somewhat similar to that shown inFIGS. 1 and 3 of U.S. Pat. No. 3,226,508 is shown in energized position.An electromagnetic actuator, generally designated 10, acts through aplunger 12 to move crossbar 14. The ends of movable contact supportblades 18 are engaged in opposed carrying slots 16 of crossbar 14. Thesupport blades carry on their opposite sides, in the position shown,contact buttons 20 and 22, each of which provides a domed contactsurface, which will be discussed hereafter. The blades 18, which provideresilient spring support for the contacts as well as acting asconductors, are cantilever supported together with their terminalelements 24 by portions of an insulating support structure 26. As bestseen in FIG. 2, similar blades are positioned in generally parallelside-by-side relationship across the width of the housing on both sidesof the actuator bar 14. The number of blades 18, and switch pairsinvolved, can, of course differ in different applications, but in thisinstance there are 12.

Also supported by the insulating support structure 26 are two other setsof blades 28 and 30 and their respective terminal members 32 and 34. Theblades 28 and 30 are also supported in cantilever fashion generallyparallel and aligned in opposition to blades 18, with their ends beingopposed to the switch contacts 22 and 20, respectively.

In the position shown in FIG. 1, the electromagnetic actuator has pulledthe rod 12 into its upper position, thereby moving bar 14 upward andwith it each of the blades 18, in opposition to the spring effect ofblades 18, so that normally open contacts 30 are closed, and thatnormally closed contacts 22 and 28 are open. Upon de-energization of theelectromagnetic device the inherent spring effect of blades 18 will urgecontacts away from blades 30 and cause normally closed contact 22 toclose against the blades 28.

For a full understanding of the novel details of the present invention,reference is made to FIGS. 3 and 4, wherein some of the details of thestructure may be better appreciated. In particular, the structure shownin the drawings has been shown in proportion to actual sizes used in apreferred embodiment of the present invention with excellent results.The spring blades 18, for supporting the contacts 20 and 22, as well asblades 28 and 30 have been made of beryllium copper but could be made ofother appropriate conductive spring material. The contacts 20 and 22 maybe made of silver, or other precious metal, or of other suitableconductive contact material, preferably plated with precious metal.Contacts 20 and 22 are respectively cylindrical buttons, which, inaccordance with the invention are provided with domed contact surfaces20a and 22a, respectively. In the embodiments shown surfaces 20a and 22aare spherical surfaces, having a /4-inch radius in their practicalapplication. Other domed surfaces, which do not provide flats, areintended to be within the scope of the invention. It is also preferredthat the surfaces be of such shape as to not even permit line contactswith the contact elements 30 and 28, respectively.

In the preferred embodiment, the bifurcated contact elements 28 and 30are of identical structure so that con-sideration of blade 30 will be aneffective description and consideration of blade 28 as well.

- As seen in FIG. 4, blade 30 is a strip of conductive spring material.The blade is bent at its electrical contact end to provide a step 36,which assures that the contact regions 38 are closer to the domedcontact 20a, so that the chance of shorting between blades 18 and 30,for example, is minimized. The end of the strip is turned upward inridge 40 to prevent any possibility that the end of the blade might diginto the contact 20. Of greatest significance is the provision of a longslot 42 extending lengthwise of the blade, preferably as shown dividingthe blade into two equal halves 44a and 44b. This slot is carried backalmost to the point where the terminal piece 34 is welded to the blade30. In practice the welding is done at two points on opposite sides ofthe circular segment cutouts 46, which act as alignment groovescooperating with cylindrical elements of insulating material extendingthroughthe insulating support structure. As a practical matter, thelength which the slot 42 has, depends upon how long it needs to be tomake spring elements 44a and 44b sufficiently long to permit therequired amount of independent twisting and flexing. As can be seen inthe schematic drawings of FIGS. 5 and 6, the thickness of each contactsupport also will be determinative of the flexibility, and particularlythe twistability, of the support elements. As is illustrated, andpossibly exaggerated, in FIG. 5, when the switch is closed the domedcontact 20a tends to move against the contact areas of 38a and 38b andthe contact areas, or surfaces at the bottom of the strip tend toflatten against the domed surface, such that a small amount ofseparation and a small amount of twisting, as well as a relatively largeamount of flexing, by companson occur.

In closing, the contacts move from the position of FIG. 6 to theposition of FIG. 5, and as closing occurs contact areas 38a and 38bslide laterally in a wiping action to assume the position shown in FIG.5. If, through some slight error, a small amount of misalignment occurs,it is not serious because each contact 38a and 38b has its separate andindependent flexible support. Thus, for example, after contact 38bengages its spring support 34b, that spring support will yield afteraccepting a certain amount of pressure. Spring support 34b will alsopermit twisting and flexing to accomodate the domed surface 20a. Untilcontact surface 38a engages, as further movement of contact carryingblade 18 occurs, flexible support 44a will yield and twist just assupport 44b continues to yield and twist until the structure comes torest.

It is of some importance that the slot 42 be kept sufficiently wide thatno interference between the two contact elements 38a and 38b will occur.It is also desirable that the areas of actual contact be plated withprecious metal, or otherwise covered with precious metal by inlaying, orany other appropriate process, in order to provide minimum contactresistance. Obviously many modifications to the structure shown arepossible within the scope of the present invention. It is contemplatedthat, depending upon the particular application, many variations in theshape and size of the domed contact will be required and manyvariations, particularly in the shape and size of the flexible springelements of the other contacts will be required. All such modificationswithin the scope of the apended claims are intended to be within thescope and spirit of the present invention.

We claim:

1. In a switch employing a pair of contacts at least one of which issupported on a resilient support with an insulating support frame tohold the contact support structure and maintain a predeterminedrelationship between said contacts and actuator means for moving atleast one contact relative to the other contact to change switchcondition, the improvement comprising providing one contact with aconvex dome shaped contact area with flat portion over said area makingthe second contact bifurcated and consisting of a pair of elementsproviding contact surfaces spaced from one another, each having a domecontact wiping edge opposed to a portion of the dome contact andsupported by a pair of flexible spring supports capable of resilientflexing and twisting such that as the contacts are urged together theflexible spring supports will continuously urge each of the contactsurfaces into wiping engagement with the dome contact, independentlyflexing, twisting and yielding as needed to accomodate the position ofthe other while maintaining good contact itself.

2. The switch of claim 1 in which at least the pair of contact wipingsurfaces of the bifurcated contact are coated with precious metal.

3. The switch of claim 2 in which the bifurcated contacts are integralwith their spring supports and comprise conductive spring sheetrnetal inan elongated strip whose thickness in the direction of principalmovement toward the dome contact is small compared to its width.

4. The switch of claim 3 in which each resilient support for each of thebifurcated contacts is sufficiently long and narrow relative to itsthickness to permit eededt isti to comod te movement nec ssar to izeepeadi i of file ffurcate contacts in goo wiriing condition with the domecontact.

5. The switch of claim 4 in which the bifurcated contacts are made froman integral strip and a slot extending part way along the strip dividesthe flexible spring supports and defines the separate supports.

UNITED STATES P ATENT OFFICE CERTIFICATE OF CORRECTION Pjatent No. 3 689'856 I Dated seggetnbgr 5, 1922 Inventofls) It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 6, line 3, after "with" insert -n0-- Signedend sealed this 8thday of October 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. c. MARSHALL DANN Commissioner of Patents Afttes-tingOfficer USCOMM-DC 60376-P69 if ".5, GOVERNMENT PRINTING OFFICE I9880-366-334.

FORM F'O-IOSO (10-69) UNITED STATES PATENT OFFICE CERTIFICATE OFCURRECTION Dated September 1972 fatent No. 3 689 856 Inventor(s) It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 6, line 3, after "with" insert --no--.

Signed and sealed this 8th day of October 1974,

(SEAL) Attest:

c. MARSHALL DANN MCCOY M. GIBS ON JR. Attesting Officer Commissloner ofPatents USCOMM-DC BO376-PBD U.S. GOVERNMENT PRINTING OFFICE: I9590-366-3SL F ORM PO-1050 (10-69)

1. In a switch employing a pair of contacts at least one of which is supported on a resilient support with an insulating support frame to hold the contact support structure and maintain a predetermined relationship between said contacts and actuator means for moving at least one contact relative to the other contact to change switch condition, the improvement comprising providing one contact with a convex dome shaped contact area with flat portion over said area making the second contact bifurcated and consisting of a pair of elements providing contact surfaces spaced from one another, each having a dome contact wiping edge opposed to a portion of the dome contact and supported by a pair of flexible spring supports capable of resilient flexing and twisting such that as the contacts are urged together the flexible spring supports will continuously urge each of the contact surfaces into wiping engagement with the dome contact, independently flexing, twisting and yielding as needed to accomodate the position of the other while maintaining good contact itself.
 2. The switch of claim 1 in which at least the pair of contact wiping surfaces of the bifurcated contact are coated with precious metal.
 3. The switch of claim 2 in which the bifurcated contacts are integral with their spring supports and comprise conductive spring sheetmetal in an elongated strip whose thickness in the direction of principal movement toward the dome contact is small compared to its width.
 4. The switch of claim 3 in which each resilient support for each of the bifurcated contacts is sufficiently long and narrow relative to its thickness to permit needed twisting to accomodate movement necessary to keep each of the bifurcated contacts in good wiping condition with the dome contact.
 5. The switch of claim 4 in which the bifurcated contacts are made from an integral strip and a slot extending part way along the strip divides the flexible spring supports and defines the separate supports. 